I hate to keep listing gripes when so much about our cruise was wonderful. But I hate that the pool on the Galaxy closed so early (7:00 each night). Since late seating isn't until 8:30, I thought the pools should stay open at least until 8:00, the same as the hot tubs. It usually doesn't take me longer than 30 minutes to get ready for dinner. I also found the pools closed before 7:00 on one night. I remember this being worse on the RCL ships.
And speaking of hot tubs, there were some people who monopolized them even though there were signs up saying to limit your time in the hot tubs to 20 minutes--some folks stayed in them for hours.
My other complaint would be with some kids who were in pools and hot tubs unsupervised. One time a lifeguard called down some young children (probably around 6-8 years old) in the pool. She told them they could not be in the pool unsupervised. They told her their nana was watching them. Nana, of course, was out cold in a deck chair.
I agree with your gripe about the kids. On Princess, though, the pools and hottubs are open 24hrs a day. My gripe with THEM is that they close the saunas at 8:00 pm, when the Steiners rip-off emporium closes (which is an entirely different gripe - Steiners, the world's leading high-pressure salespeople)